1. Technical Field
This invention relates to ignition systems for internal combustion engines.
2. Prior Art
Distributorless ignition systems (DIS) are known and described in, for example, in "Ignition and Timing Systems", by K. L. Longstaff, Institution of Electrical Engineers Publication No. 181 (1979) entitled Automotive Electronics and in a Society of Automotive Engineers Technical Paper 780327 entitled "A Distributorless Ignition System--Solid State Ignition High Voltage Distribution with Low RFI Emissions" by J. R. Asik, D. F. Moyer, and W. G. Rado, 1978. The second article is devoted to a specific type of DIS utilizing a single ignition coil having two primary windings, a floating secondary winding, and four high voltage diodes to steer the ignition voltages to the proper spark plugs. Each high voltage terminal is connected to two spark plugs through a pair of high voltage diodes arranged in opposite polarity. This DIS is suitable for igniting a four cylinder engine. The first article referenced above is devoted to review of various types of ignition systems, including DIS. An alternate DIS design described for four cylinder application consists of two ignition coils, each having a single primary winding and a floating secondary winding. Each high voltage terminal is connected to a single spark plug and each ignition coil primary is alternately energized and quickly de-energized, producing opposite polarity ignition voltages at each coil terminal. As a result, pairs of spark plugs are alternately fired, with each firing pair occurring in a compression or exhaust stroke and thereby providing the proper ignition to the engine. For both types of DIS described, two-phased signals are required for each electronic module. Such signals can be generated by an electronic engine control.
U.S. Pat. No. 4,216,755 issued to Ordines discloses a distributorless ignition system for a four cylinder engine which includes a discharge module. The discharge module controls a Darlington pair which is in series with the primary windings of the ignition coil. Other related patents include U.S. Pat. Nos. 4,033,316 issued to Birchenough and 4,136,301 issued to Shimojo.
The prior art also teaches increasing the energy of the spark. When using very lean air/fuel mixtures it is known that increasing spark duration or intensity is desirable to improve combustion. For example, U.S. Pat. No. 4,191,912 issued to Gerry teaches a distributorless ignition system with a relatively high frequency alternating current power source to enable large quantities of energy to be fed to each igniter so that the fuel in the engine will be more completely combusted and exhaust contaminants reduced. There still remains a need for an improved apparatus for increasing spark energy in a distributorless ignition system.